The present invention relates to methods for making semiconductor devices, in particular, semiconductor devices that include high-k gate dielectric layers.
MOS field-effect transistors with very thin silicon dioxide based gate dielectrics may experience unacceptable gate leakage currents. Forming the gate dielectric from certain high-k dielectric materials, instead of silicon dioxide, can reduce gate leakage. Such a dielectric may not, however, be compatible with polysiliconxe2x80x94the preferred material for making the device""s gate electrode.
The electron mobility on high-k films may be notably inferior to the electron mobility on silicon dioxide or silicon oxynitride films. In addition, when such a high-k film comprises an oxide, it may manifest oxygen vacancies and excess impurity levels. Oxygen vacancies may permit undesirable interaction between the high-k film and the gate electrode. When the gate electrode comprises polysilicon, such interaction may alter the electrode""s workfunction or cause the device to short through the dielectric.
Accordingly, there is a need for an improved process for making a semiconductor device that includes a high-k gate dielectric. There is a need for such a process for producing a device that demonstrates acceptable electron mobility on the gate dielectric. There is a need for a process for forming a very thin high-k gate dielectric that improves the interface between the high-k film and the gate electrode by minimizing oxygen vacancies in the high-k film. The method of the present invention provides such a process.